These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The crocobearamoose's rap number in the third movie.
Canon Sue: Fred is loved by pretty much everyone, bar a few antagonists.
Interestingly, in the pre-nickelodian era Fred was hated by every character, even Bertha.
Creator's Pet: Fred himself has a humongous Hatedom, but sponsors and Nickelodeon seems to love the guy, giving him a grand total of three movies (the first of which was a colossal bomb and has a 0% rating on Rotten Tomatoes) and an animated series.
Not to mention Marvin Marvin starring the same actor, which is basically Fred as an alien.
One-Scene Wonder: John Cena's appearance in his film was pretty funny, and to most the only funny bit in the film.
Nightmare Fuel: In recent episodes, Fred is harassed by an extremely creepy man named Claudio. In Fred Gets Kidnapped by Claudio, he is introduced by randomly breaking into Fred's house, kidnapping him, and locking him in a pet carrier, and then when Fred's mother catches Claudio, she allows him to stay because he will pay her, despite the fact that he just kidnapped and caged her son. In the next episode, Fred is Left Alone with Claudio, Fred's mother LEAVES FRED ALONE WITH HIM and Claudio continues to do more creepy and outright messed-up things to harass Fred. Brr..
Surprisingly Improved Sequel: The first two Fred movies were pretty forgettable, the third though is actually considered quite good by the fanbase. Helped that it got a few well known names attached to it.
Fred comes off as kind of racist at some points. In the first movie Judy moves and an Asian family moves into her house, and Fred immediately jumps to the conclusion that evil Asian people kidnapped her. Later when he runs into a Mexican guy he assumes he's a space alien because he doesn't understand Spanish.
Note that this is the intention of the creators. Whereas he calls forth the audience's sympathy is a massive YMMV, especially given his pettiness and selfishness. Then again though, he is a child after all.
Memetic Molester: Mr. Devlin. MikeJ's reaction to Devlin inviting Fred to his house ("Is Fred going to be molested?) is very accurate, as that's eerily how the scene plays.
Fan-Preferred Couple: A lot of Fred fans were disappointed Fred ended up with Judy in the end and not Bertha. Incidentally there were four endings written for the movie, one of which being Fred and Bertha becoming a couple.